Since extraesophageal space contains loose connective tissue and saline can permeate into extraesophageal space and separate esophagus from adjacent organ; furthermore, saline serves as an EUS contrast agent (negative) and is detected by EUS.Therefore, we envisaged that if saline is directly injected into extraesophageal space, the separation between the esophageal adventitia and its adjacent organs (especially the thoracic aorta, arcus aortae, and tracheal bifurcation) can be observed by EUS. In our recent experiment in canine model, guided by EUS,extraesophageal saline injection was successfully conducted and saline separated esophageal adventitia from adjacent organs including thoracic aorta, arcus aortae, trachea and bronchial bifurcation without any complication.